Method for making a module comprising at least an electronic component

ABSTRACT

This aim is reached by a method for manufacturing an electronic module comprising at least one electronic component ( 4 ) and a layer formed by a binder, the electronic component ( 4 ) presents a visible face on the surface of the module, characterized in that one places a frame ( 3 ) on a protection sheet ( 2 ) placed on a base plate ( 1 ). At least one electronic component ( 4 ) is then placed on the protection sheet ( 2 ) and inside the frame ( 3 ). A pressing plate ( 6 ) is leant on the outline of the frame ( 3 ) before the introduction of a binder through orifices ( 5 ) pierced in the frame ( 3 ). This binder encapsulates the electronic component ( 4 ) by filling the space defined by the frame ( 3 ), the protection sheet ( 2 ) and the pressing plate ( 6 ). After solidification of the binder, the base plate ( 1 ) and the pressing plate ( 6 ) are removed.

The present invention belongs to the field of manufacturing processes ofan electronic module comprising a layer formed by a binder and at leastone electronic component.

The invention concerns modules made by filling a mould with a binder,these modules including at least one electronic component. An electroniccomponent is defined here as an element such a chip, a transponder, anintegrated circuit, a capacitance, a resistor, a fuse, a battery, solarcells, a display, a fingertip controller, a switch, a keyboard, or allother similar element. The electronic component can be also anelectronic circuit formed by the connection of a plurality of elementssuch as quoted above.

The electronic modules made like this include at least one planar faceand a second face generally parallel to the first one from where flushesthe visible part of the electronic component. Their outline is of anyshape. Their thickness is close to the one of the highest electroniccomponent. The components are entirely or partially embedded in a rigidinsulating mass formed by a solidified binder. The module external shapeis defined by the mould in which is introduced the binder during themanufacture of the module.

In general, these modules are destined to applications, which require agreat mechanical sturdiness, a certain resistance to environmentconstraints (corrosion, pressure, temperature, humidity) andinviolability (difficulty of dismounting or of piracy). These modulescan, for example, constitute means of control, of identification, ofregistration/restitution of sophisticated data or apparatuses componentssuch as computers, control automates, electrical power supply blocksetc.

The subject of this invention focuses particularly on the manufacturemethod of these modules. It is known by those skilled in the art,modules obtained by encapsulation of electronic circuits processes wherea binding is flowed in a mould containing the circuit. After hardeningof the binder, the module is extracted from the mould. The shape and thesize of the module are defined by those given to the mould. For example,document U.S. Pat. No. 5,416,358 describes a flat module, which includesa frame surrounding a printed circuit board on which electroniccomponents are mounted. The frame is provided of lateral orificesdestined to the injection of filling resin (binder). Each face of theframe is covered by at least one insulating sheet, which can include adecoration. The module does not include any apparent component on one ofits faces. All the components are mounted on a printed circuit, which isplaced in the frame in order to be encapsulated by a resin.

The documents U.S. Pat. No. 4,961,893 and FR2630843 describe a processof over molding a chip card using a mould in two parts, one fixed andone moving part, defining an impression, which gives the external shapeof the card. A support sheet in insulating material is clamped betweenthe two parts of the mould making a separation of the volume formed bythe cavities of the fixed and the moving parts when the mould is closed.Electronic components are glued on the face of the support sheetdirected to the fixed part of the mould. A plastic filling material isinjected, through adequate orifices, in the volume delimited by thefixed part and the support sheet. The latter is then pushed against thewalls of the cavity of the moving part under the pressure of theinjected material. The components are then partially embedded in themass of the filling material. During the extraction of the card from themould, the support sheet adheres on the moving part of the mould. Thefaces of components previously glued on the support sheet appear then onthe face of the card.

This method is particularly adapted to the manufacture of low thicknesscards including at least one component presenting an access face such asa contacts module. A relatively high pressure is then necessary for theinjection of the filling material in order to push the support sheet, onwhich are glued the components, against the inner walls of the mould.

In an embodiment of the method described above, the positioning of thecomponents is made by air suction through orifices made in the mould inparticular on the two planar faces. The application of this method needsa sophisticated mould connected to an air suction system, which requiresa difficult installation.

These known processes need onerous and relatively long steps, whichprevent a very large volume production of modules. Moreover,difficulties appear at the level of the electronic components holdingduring the preparation phases of the mould and during the flowing of thebinder. In fact, some components must be placed in an accurate positionon the final module, especially when a face of the component appears onone of the module faces. For example, a display, solar cells and anintegrated circuit have a position determined namely by the foreseenfunctioning of the module.

Another method uses a positioning structure including windows in whichthe components are inserted. This structure is placed in the mouldcavity before pouring the binder.

According to the document EP0650620, a method is described using acompressible positioning structure, which holds the electroniccomponents between two pressing plates during the binder injection.

The methods using a positioning structure are well adapted for modulesincluding electronic components entirely embedded in the binding mass asfor example in the case of the contactless chip cards.

Some modules include electronic components from which one face mustappear on the surface of the module. These cases arise for componentssuch as a display, solar cells, keyboard keys, etc. The methodsdescribed above are difficult to apply because the binder can flow onthe surface of the component, which must remain visible on the face ofthe module. In fact a gap can subsist between the face of the componentand the bottom of the mould cavity. This gap is formed by flatnessshortcomings of the component surface and the mould inner face againstwhich the component is pressed. The binder then flows in this gap bycapillarity effect, or by suction if the component is maintained in themould by vacuum. The useful face of the concerned component is thendamaged.

The aim of this invention is to avoid the drawbacks described above byoffering a low cost method of manufacturing modules allowing a largevolume production. This concerns in particular the positioning of theelectronic components in the mould which must be maintained during thewhole manufacture process of the module by guaranteeing the integrity ofthe visible surface of said components on one and/or the other face ofthe module.

This aim is reached by a method for manufacturing a module comprising atleast one electronic component and a layer formed by a binder, theelectronic component being partially embedded in a rigid mass formed bythe solidified binder, presents a visible face on the module surface,the outer faces of said module being sensibly flat, characterized inthat it includes the following steps:

-   -   placing of a protection sheet on a base plate,    -   placing a frame on said protection sheet, said frame defines the        final shape of the module; the thickness of the frame is        determined by the maximum height of the electronic component,    -   putting on the protection sheet and inside the frame at least        one electronic component, the position of said component being        maintained by adhesion on the protection sheet,    -   leaning a pressing plate on the outline of the frame,    -   introducing a binder between the protection sheet and the        pressing plate through orifices provided for that purpose in the        frame, said binder encapsulating the electronic component and        filling the space defined by the frame, the protection sheet and        the pressing plate,    -   solidifying the binder, said binder forming a rigid layer        maintaining the electronic component,    -   removing the base plate and the pressing plate after        solidification of the binder.

The protection sheet used in the above method consists of a plasticmaterial film in general covered by an adhesive substance on all or partof its surface. It has the particularity to offer a provisional andnon-permanent gluing of the components applied to its surface.Furthermore, this sheet applies on the surface of the component in sucha way to obstruct all the residual gaps, which could let the binder passbetween the protection sheet and the surface of the component. Theremoval of this sheet, at the end of the module manufacturing processremains easy; the adhesive layer of the film surface does not leave anytrace on the component.

Another embodiment of the protection sheet is free of adhesive substancethanks to the fact that it consists of a non-absorbing sheet, forexample made on rubber or silicone. The electronic component, applied onthe sheet by pressure, embeds lightly in the sheet thickness, whichassures the impermeability to the binder necessary for the componentsurface protection. This pressure is obtained with the placement of acompressible material placed on the electronic component and which comesin support on the pressing plate.

This method facilitates furthermore the manufacture of modules inimportant sets by allowing a superposition of the moulds. This advantageappears by the preparation of an elements stacking: base plate,protection sheet, frame, component, pressing plate, before the binderinjection step.

According to a first embodiment of the method, a compressible materialcan be superimposed on the electronic component in order to improve itsholding when its attachment on the protection sheet proves insufficient.This case occurs particularly for a relatively high weight componentsuch as a battery or a display placed away from the module edges,respectively frame edges. Furthermore, during the manufacture in series,for practical reasons of assembly and to limit the encumbrance, themoulds are preferably arranged vertically. The component must not thusleave its position under the effect of gravity.

According to another embodiment of the method, an insulating materialsheet with windows, here called positioning structure, can be placed ofon the protection sheet.

The electronic components are inserted in the windows and one of thecomponents faces is applied against the protection sheet. The windowssize corresponds to the one of the components outline. Thissupplementary maintenance mean would be used for example, for a largenumber of uneven size components. In this embodiment, a compressiblematerial as described above can also cover the set of the components inorder to improve their holding in the mould.

The invention will be better understood thanks to the following detaileddescription referring to the attached drawings given as a non-limitativeexample, in which:

FIG. 1 represents a general view of a layout serving to the modulemanufacture

FIG. 2 shows a section of the layout of FIG. 1.

FIG. 3 represents a general view of a layout with a compressiblematerial.

FIG. 4 shows a section of the layout of FIG. 2.

FIG. 5 represents a general view of a layout with a compressiblematerial displaced in a semi-shell

FIG. 6 shows a section of the layout of FIG. 5.

FIG. 7 shows an embodiment of FIG. 4 with a compressible materialwidespread.

FIG. 8 shows a section of a layout including a positioning structure.

FIG. 9 shows a section of a layout including a positioning structure anda compressible material.

FIG. 10 shows a section of a layout including a positioning structureinside the frame.

FIG. 11 shows a layout with two superimposed components separated by acompressible material.

FIG. 1 shows an example of elements layout serving to the modulemanufacture. A protection sheet (2) is placed on a base plate (1). Aframe (3) is placed on the protection sheet (2). An electronic component(4) is placed inside the frame (3) to the location predetermined by themodule configuration. This component adheres to the protection sheet(2), which maintains its position during all the manufacture processphases. The frame (3) defines the final shape of the module; itsthickness is at least equal to the maximum height of the component (4).

FIG. 2 is a section according to the axis A-A of the layout of FIG. 1,on which a pressing plate (6) is placed on the frame (3). The base plate(1), the frame and the pressing plate (6) constitute a mould. The binderis injected through the orifices (5) made for that purpose in the frame(3) and fills all the space around the component (4) delimited by theinner walls of the mould. The latter are formed by the protection sheet(2) covering the base plate (1), the inner walls of the frame (3) andthe inner face of the pressing plate (6). In general, the thickness ofthe frame is greater than the height of the component in such a way itleaves a space between the latter and the pressing plate. The binderthen can cover the face thus disengaged of the component.

FIG. 3 shows an embodiment of the method according to the invention inwhich a compressible material (7) is superimposed on the component (4).The thickness of the compressible material (7) is chosen in such a waythat the total height reached by the component covered by thecompressible material is either equal or greater than the thickness ofthe frame (3).

FIG. 4 represents a section of the layout of FIG. 3 according to theaxis A-A with the pressing plate (6) exerting a pressure on thecomponent (4) through the compressible material (7). The maintenance ofthe electronic component (4) in the mould is then improved. Thecompressible material (7) is constituted by a foam plastic material, awaved sheet or other material having adequate elasticity. The binderintroduced in the mould is absorbed by this in general porous materiallike the foam for example, and fills the free space in the mould.

FIG. 5 shows an embodiment of FIG. 3 where the compressible material (7)is placed inside a semi-shell (10) that is placed on the electroniccomponent (4).

FIG. 6 represents a section of the layout of FIG. 5 according to theaxis A-A with the pressing plate (6). The height of the semi-shell walls(10) corresponds to the height of the space separating the electroniccomponent (4) from the pressing plate (6). A pressure is exerted on thecomponent (4) by the pressing plate (6) and through the compressiblematerial (7) whose thickness is greater than the height of thesemi-shell walls (10). The binder introduced in the mould is spread inall the free space delimited by walls of the frame (3), the base (1) andpressing (6) plates and the walls of the semi-shell (10). The binderthus does not penetrate inside the semi-shell (10) where thecompressible material (7) is lodged. After the hardening of the binder,the base (1) and pressing (6) plates are dismounted and the compressiblematerial (7) is removed from the inside of the semi-shell (10). Themodule so obtained includes on one of its faces a cavity formed by thesemi-shell (10). This cavity can serve for housing a battery forexample, the bottom of the semi-shell includes openings to let passcontacts placed on the internal face of the electronic component (4).

FIG. 7 represents a case where the size of the compressible material (9)is chosen in order to correspond to the one of the inner outline of theframe (3).

FIG. 8 shows an embodiment where several electronic components (4, 4′,4″) of small size are housed in windows formed in an insulating materialsheet (8) called positioning structure. This structure (8), placed onthe protection sheet (2) groups components (4, 4′, 4″) in a well-definedposition by preventing their dispersion during the injection of thebinder in the mould. The surface of this positioning structure (8)occupies all or part of the surface of the protection sheet (2), theframe (3) being placed on the positioning structure (8). The externalsurface of the latter can carry a decoration appearing on the finishedmodule. When the positioning structure (8) exceeds the external outlineof the frame (3), a finishing step of the module outline is necessary bystamping it for example.

FIG. 9 shows an embodiment of FIG. 6 where the components (4, 4′, 4″)are covered by a compressible material (9) occupying the whole surfacedelimited with the inner outline of the frame (3). The components (4,4′, 4″) maintaining against the protection sheet (2) is thus improved bythe pressure exerted on the pressing plate (6) acting on thecompressible material (9).

FIG. 10 shows an embodiment where the positioning structure (8) occupiesall or part of the surface delimited by the inner outline of the frame(3); the latter being placed on the protection sheet (2). In anembodiment not illustrated, a compressible material can cover theelectronic components in order to improve the maintenance of the setcomponents—positioning structure through the pressure on the pressingplate (6).

FIG. 11 shows a layout for the manufacturing of a module includingelectronic components (4, 4′) whose face must appear on each face of themodule. A first protection sheet (2) is placed on the base plate (1).The frame (3) is placed on the protection sheet (2). Inside the frame(3) a first component (4) is positioned on which the compressiblematerial (11) is superimposed. A second component (4′) is positioned onthe compressible material (11) on which a second protection sheet (2′)is placed. This sheet has a surface at least equivalent to the onedelimited by the external outline of the frame (3) in such a way toavoid the flowing of binder on the component face (4′), which mustappear on the module face. The total height reached by thesuperimposition of the components (4, 4′) and the compressible material(11) exceeds the frame thickness. The compressible material thickness isthus chosen in order to assure sufficient pressure on the set with thepressing plate (6) that closes the mould.

Another embodiment not illustrated of the method consists in:

-   -   placing the frame (3) on the base plate (1),    -   putting the protection sheet (2) inside the frame (3), the        surface of the protection sheet (2) occupies all or part of the        surface delimited by the inner outline of the frame (3). The        protection sheet (2) adheres to the base plate for example by        the mean of glue or by electrostatic attraction.    -   putting on the protection sheet at least one electronic        component (4)    -   leaning the pressing plate (6) on the outline of the frame in        order to close the mould.

The binder is then introduced through the orifices (5) of the frame (3),and then solidified.

In order to prevent the binder infiltration on the component useful facewhich must appear on the surface of the module, the size of theprotection sheet must be equal or greater than the one of the component,the latter being entirely placed on the protection sheet.

This embodiment can apply for example in the case of a module where thecomponent visible surface must be in a light recess compared with thesurface of the module. This recess is equivalent to the thickness of theprotection sheet placed inside the frame without therefore occupying thewhole inner surface of said frame.

After the solidification of the binder, the mould is dismounted byremoval of the base (1) and pressing (6) plates. The removal of theframe (3) is optional and depends on the desired shape and/or the finishof the module. The protection sheet (2) is withdrawn at last, eitherbefore the finish of the module faces, or after the assembly of themodule in an apparatus for example. This sheet can serve as protectionof the component during the manipulations of the module. For example, itprevents stripes on the transparent surface of a display.

A facultative final step of the manufacture process of the modules aftertheir removal from the mould consists in applying a plastic materialfilm on one or each face of the module. This film, serving asdecoration, includes the necessary windows to let appear the componentsuseful faces such as a display, solar cells, keys, etc.

1-18. (canceled).
 19. Method for manufacturing a module comprising atleast one electronic component and a layer formed by a binder, theelectronic component being partially embedded in a rigid mass formed bythe solidified binder, presents a visible face on the module surface,the outer faces of said module being sensibly flat, characterized inthat it includes the following steps: placing of a protection sheet on abase plate, placing a frame on said protection sheet, said frame definesthe final shape of the module; the thickness of the frame is determinedby the maximum height of the electronic component, putting on theprotection sheet and inside the frame at least one electronic component,the position of said component being maintained by adhesion on theprotection sheet, superimposing a compressible material on theelectronic component to cover all or part of said electronic component,leaning a pressing plate on the outline of the frame, said plateexerting a pressure on the compressible material, introducing a binderbetween the protection sheet and the pressing plate through orificesprovided for that purpose in the frame, said binder encapsulating theelectronic component and filling the space defined by the frame, theprotection sheet and the pressing plate, solidifying the binder, saidbinder forming a rigid layer maintaining the electronic component,removing the base plate and the pressing plate after solidification ofthe binder.
 20. Method for manufacturing according to claim 19,characterized in that the protection sheet includes an adhesivesubstance on all or part of its surface, the electronic component beingplaced on the adhesive zones of the protection sheet surface.
 21. Methodfor manufacturing according to claim 19, characterized in that the frameis placed on the base plate, the protection sheet is placed inside theframe, said sheet, occupying all or part of the surface delimited by theinner outline of the frame, is maintained by adhesion on the base plate,the electronic component is entirely placed on the protection sheet,said sheet maintains the component by adhesion.
 22. Method formanufacturing according to claim 19, characterized in that the thicknessof the compressible material is determined in such a way to make thepressure applied on the pressing plate act on the electronic component.23. Method for manufacturing according to claim 19, characterized inthat the compressible material is placed inside a semi-shell, saidsemi-shell is placed on the electronic component, the height of thesemi-shell walls corresponding to the height of the space separating theelectronic component from the pressing plate, the binder introduced bythe orifices of the frame spreads in free space delimited by the framewalls, the base and pressing plates and the semi-shell walls, saidbinder does not penetrate inside the semi-shell where is thecompressible material, after solidification of the binder, the base andpressing plates are dismounted and the compressible material is removedfrom the inside of the semi-shell.
 24. Method for manufacturingaccording to claim 22, characterized in that the compressible materialoccupies the whole surface delimited by the inner outline of the frame.25. Method for manufacturing according to claim 19, characterized inthat a positioning structure is placed on the protection sheet, saidpositioning structure occupies all or part of the surface of theprotection sheet, said structure includes at least one window in whichis housed the electronic component, said component is maintained by theprotection sheet and the positioning structure.
 26. Method formanufacturing according to claim 25, characterized in that the frame isplaced on the positioning structure and in that a final step, aftersolidification of the binder, consists in adjusting the outline of saidplacement structure to the final module size.
 27. Method formanufacturing according to claim 25, characterized in that thepositioning structure occupies all or part of the surface of theprotection sheet delimited by the inner outline of the frame, said framebeing placed on the protection sheet.
 28. Method for manufacturingaccording to claim 25, characterized in that the frame is integral withthe positioning structure, the set thus formed constituting a cavity,the bottom of said cavity corresponding to the positioning structure andthe side walls corresponding to the frame.
 29. Method for manufacturingaccording to claim 25, characterized in that the external face of thepositioning structure is used as decoration.
 30. Method formanufacturing according to claim 25, characterized in that acompressible material is superimposed on the positioning structure inwhich is housed the electronic component.
 31. Manufacture process of anelectronic module, according to claim 19, characterized in that a secondelectronic component is superimposed on the first electronic component,said components are separated by a compressible material, the secondcomponent is covered by a second protection sheet in support on thepressing plate, said second sheet having a surface at least equivalentto the one delimited by the external outline of the frame.
 32. Methodfor manufacturing according to claim 19, characterized in that the frameis removed after solidification of the binder and the opening of thebase and pressing plates.
 33. Method for manufacturing of an electronicmodule according to claim 19, characterized in that the frame is a partof the module and is kept after solidification of the binder and theopening of the base and pressing plates.
 34. Method for manufacturingaccording to claim 19, characterized in that the protection sheet isremoved only during the final use of the module, said sheet protects theelectronic component during module manipulations.
 35. Method formanufacturing of an electronic module, according to claim 19,characterized in that a plastic material film is applied on one or eachface of the finished module, said film, serving as decoration, includesthe windows necessary to let appear the electronic components usefulfaces.